In recent years, the proportion of breeded fish which accounts in the catch is being increased, and importance of the fish breeding tends to increase in future.
At present, in the case of fresh-water fish, feeds used are for the most part, mixed feeds. On the other hand, in the case of sea-water fish, living baits are mainly used, and the sea-water fish are breeded with moist pellets comprising a mixture of a mixed feed and a living bait. However, even in the case of the sea-water fish, when living baits are used, there have recently been caused problems in the contamination of sea-water, quality stability, and workability of bait feeding. Accordingly, complete mixed feeds which are free from these problems partly started to be used.
However, since the mixed feeds involve such defects that the cost is high and the taste is bad as compared with those of living baits, the fact is that they are hard to wide spread except for fry. At present, in order to improve the preference for food of fish, fish internal organ extracts, krills, etc. are used, since there are problems in the quality and the feeding stability, and satisfactory effects have not yet been obtained.